Temperature-indicating device



Nov. 13,1928. 1,691,133

H. SCHLAICH @EMPERATURE INDEECATING DEVICE Filed Feb. 23, 1918 W IIIIIIIIIIII'W' I [1N VIEW TOR Patented Nov. 13, 1928.

HERMAN SGHLAICH, OF BROOKLYN, NEW YORK.

TEMPERATURE-INDICATING DEVICE.-

Applicatiorl filed February 23, 1918. Serial No. 218,801.

This invention relates to improvements in gages and is more particularly designed to -provide aninstrument for the indication of i temperatures in connection w'th the internal a combustion motors of aeroplanes or other vehicles, such as automobiles or motorboats The advantages of the useof an instrument for indicating the thern'ial condition of internal combustion engines are well known but the problem of devising a sat'sfactory and accurate instrument which will meet the requirements of practice is diflicult as the conditions of use introduce numerous sources oferror which must be compensated for or from which the instrument must be rendered immune. Thus an instrulmuit utilized upon a motor-driven vehicle is necessarily subjected to severe vibration and must be of sucha character as not to be thereby prevented either from indicat-in accurately or from being substantially dea beat; so that it may be eas'ly read. Such an instrument. must also be of such a character that its indications will be accurate in spite parts of the instrument other than the temperature res onsive element thereof may be subjected. t is'also important that the instrument shall not be subjected to error due to varying atmospheric pressure, this condition being vital where the instrument is intended for aeroplane use owing to the wide range of atmospheric pressure due to altitude. H i

The pr'ncipal object of the present invention is to provide an instrument which is not sensitive to'or which is duly compensated for the effects of the various factors named so that it shall be capable of use for the ac curatemeasurement of the temperatures of 'the motors of aeroplanes and other vehicles and for other purposes, and which shall be light, compact, durable and present no manufacturing diilicult'es which would pre-,

' vent it from being manufactured at a reasonable cost and upon a quantity production basis. y

The nature of the improvements by'which I secure the foregoing and other objects w ll be best be understood in connection with the description of one specific-embod ment 0fthe invention which I have chosen for ilof variable temperature conditions to which verse sectional view thereof. Figure 3 is a diagrammatic view illustrating one way in which the instrument may be applied .for the measurement of temperatures in the cooling system of an aeroplane engine. Figure lis a cross section on a large scale of an improved form of capillary tube and easing which may be employed. Figure 5 is a de' tail view of a part of the compensating coil showing how adjustment thereof may be made by soldering portions of the coil together.

The particular type of instrument which I have chosen to illustrate the principle of my invention and the best mode now known to me for performing the same, comprises what is known as a distance type thermom- "eter, which I have shown applied to the cooling system of an aeroplane motor. Referring to Figure 3, this type of instrument comprises a temperature responsive element or bulb 1,-wl1ich is to be placed in such a location as to be subjected to the tempera ture to beimeasured, an ind cating instrument or gage 2 and a connection in the form of a small bore tube or capillary 3 between these two elements. As illustrated, the bulb 1 is inserted in the return pipe 4 which conveys the heated cooling fluid from the cylinder jackets 5 of the engine to the upper part of the radiator 6, the water flowing downwardly through the radiator and vbecoming cooled, after which it returns to the cylinder jackets through the inlet pipe 7. Circula-' tion of water may be maintained in any suitable manner as by -means of a circulating pump 8. The mode of operation and advantages of an instrument havingthe temperature responsive element thus located are fully set forth in the patent to Boyce No. 1,206,783, and I prefer this location for such element, but itis to be understood that the use of this invention isv not limited to this location. The gage 2 is located in any suit able posit'on for observation by the driver of the vehicle, preferably upon the vehicle dash or instrument-board 9.

The gage 2 comprises a pressure sensitive element and indicating or recording "means actuated thereby. As illustrated in Figures lustration in the accompanying drawings f t-w! 1 and 2, the pressure sensitive element is in the form of a multiple coiled flattened tube or Bourdon spring 10, one end of which is in communication with the end of the tube 3 and is mounted upona suitable fixed support; while the free end of the flattened tubeor spring is closed. For reasons which may without interfering with the proper operation of the spring, coil the same into a compound helix having a plurality of turns pro ressing in one direction axially and then ii in the opposite axialdirection, either inside or outside of the first series of helical turns, all the turns, however, being in the same circumferential direction. As illustrated, the fixed end of the Bourdon coil or spring is carried in a forked bracket 11 projecting from the base plate 12. Starting from this end, .the coil is wound into a plurality ,of turns forming an outer helix 13 progressing away from the base 12, then through an intermediate turn 14 into a second series of turns 15 comprising a helix concentric with the helix 13 but of smaller diameter and progressing in the opposite axial direction, to the closed free end of the coil at 16. All of the turns of the coil, however, are formed in the same circumferential direction, so that the entire coil acts as a unit. In accordance with the well-known action of Bourdon springs, variations in pressure within the coil will tend to cause it to unroll when the pressure is increased or permit it to roll up when the pressure is decreased, and as the effect of the various turns is cumulative throughout the coil, a very considerable movement of the free end of the coil may be secured. In the instrument shown the Bourdon spring or coil 10, capillary tube 3 and bulb 1 are completely filled with a liquid Which is preferably under considerable initial pressure. Any suitable liquid may be employed, preferably alcohol, as this possesses the necessary thermal qualities, does not freeze at ordinary temperatures, and does not tend to amalgamat-e with the 'metal of which passages of the instrument are constructed, thus permitting the use of brass or copper, which would not be a possible were mercury utilized.

In practice the coil 10 is wound so that the -tur ns thereof receive a permanent set,

and will normally act to hold the free end of the coil in a definite fixed position. When, under the influence of the hquid in the coil and in the bulb 1 and tube 3, the coil 10 unwinds, the free end thereof is moved away from this position; and as soon as the, liquid ceases to affect the coil 10 in such a way the turns 13, 14, and 15, are constrained by their own elasticity. or resiliency, to roll up again and restore the free end of the coiljto its starting point.- This mode of operation will be more fully exp lained hereinafter. 7 I l The ,baseplate 12 to which the fixed end of the Bourdon spring is secured forms the back or'bottom of the instrument casing 20. The latter in the particular construction illustrated is provided with an intermediate flange 21 adapted to be attached to the dash or instrument board 9, the forward end of the casing projecting beyond this flange and being provided with a screw thread 22 and with a rounded shoulder or seat 23. A dial plate 24 is provided at the front of the casing, this dial plate being made to abut against a ring adapted to fit in thefront end of the casing and being outwardly curved or flared so as to rest snugly upon the seat 23. The front of the instrument is closed by a glass or crystal 26, which is adapted to be clamped against the periphery is located in the space between the crystal 1 and dial plate, the hand being mounted upon an arbor 31 journaled at its front end in a bushing 82 in the dial plate and its rear end in a bearing plate 33 secured to a boss 34 on the base plate 12 in any suitable manner, as by means of screws 35, this boss 34 being provided with a central recess 36 to receive the projecting end of the arbor.

The free end 16 of-the Bourdon spring or coil has attachedito it one. end of a lever 37, which lever is journalled to rotate on the arbor The opposite end of the lever is attached. to one end 38 of a compensating coil 39, the other end of which 40 is fixed to the arbor 31. The compensating coil 39 is preferably formed of super-imposed and firmly united layers-of materials having differe'nt co-eflicientsof expansion, such for in-y stance, an outer layer 41 of brass and the The invenlar materials as any other construction of thermo-responsive element having the desired properties may be employed. When subjected to changes in temperature, the action of a bimetallic coil of this character will be to wind or unwind somewhat due 'to differences in expansion of the'layers of material of-which the coil is made and as the coil constitutes the operative connection between the free endof the Bourdon spring 16 and the arbor carrying the indicating hand, it will be seen that the winding or unwinding of the compensating coil will produc'e'a relative adjustment of position between the index hand and the end of the Bourdon spring.

Specifically, arelativel high temperature in the vicinity of the' which might cause this spring to unwind more, than is warranted'by the thermal condition of the cooling agent in the engine ourdon spring 10, i

lil)

I preferably cross section. The tube-3 is preferably enclosed in a casing lt'fconslst-ing of a circusjacket .5. and move the pointer 30 too much, so that the pointer would indicate a temperature higher than the true temperature of the cooling agent; will affect the compensating coil 39 so as to cause it to roll up, and lessen the movement of the pointer 30. As a result the pointer will indicate the real temperature of the cooling agent and no more. Also if the temperature around the spring 10 be relatively low, as on very cold (lays, the springlO by itself might indicate a temperature less than that of the cooling agent; but in this instance, the coil 39 unwinds and tends to increase the swing of the pointer, giving the same accuracy as before.

A'useful feature of construction which I employ consists in forming around the opening in the back plate or casing through which the capillary tube is led into the instrui'nent acountersink or depression having an annular convex rounded wall 43 merging into the cylindrical wall of an opening 44, which fits the capillary tube or its casing closely. The rounded wall l3 permits thetube to be led into the instrument from any direction without danger of putting a short bend or kink therein which might result in breaking the tube or flattening it out so as to interfere withthe free communication therethrough.

While any suitable form of capillary tube may be employed, I preferably utilize the construction described and claimed in my application Serial No. 227,75'l, filed April 10. 1918. and illustrated in detail in Figure 4. As here shown the capillary tube/3 is formed from a circular tube by longitudinally forcing in the walls thereof at a plurality of circumferentially spaced points as indicated at 45, ther-eby'producing a tube having what may be termed a Fstarlike cross section. In this way the cross-seetioual area of the tube is materially reduced and it is possible to producea tube having a capillary bore of much less area than can be attained by ordinary processes of drawing. At the same time, the form of the tube is such that it is not easily flattened out in such a way as to completely close the passage therethrough for the reason that even it' the depressed portions of the tube come into contact, there will almost invariably re main a passage through some partof the 'lar tube of copper or other flexible material of slightly larger diameter than the capillary'tube: The tubeS may advantageously be introduced in the tube 46 at the same time that it is rolled in the star-likeform as explained in my' application above referred The starlike form of the tube 3 lends Lil self particularly to encasement in this fmanner as it will bear against the encasing tube only at one or more of the points l'l'.

The transmission of heat from onetube to the other is thus mlnnnized so that the encasmg'tube, as well as forming a mechanical protection for the capillary tube, also pro- 'vides an air space between the two tubes to define tubing of the smallest capacities,

in which the bore is of hair-like dimensions. Moreover, in the distance type instrument art, to which the present invention relates, the term capillary or capillary tube has an accepted meaning as designating the pressure transmitting tubing, connecting the bulb of the instrument with the instrument head or indicating parts proper which latter usually consists of a Bourdon spring which is so shaped as to change its form in response to changes in internal pressure and which therefore is necessarily of much greater than capillary dimensions as that term is herein employed.

A useful feature of construction of the casing shown consists in providing the back plate 12 with two supports 48 that extend from the inner-face of the back plate to wards the glass 26. To these supports the dial Qt is fixed; and the supports will be long enough to make the 'dial contact with the paratus described and'as'suming that't eon-- stemgin e is at rest, the water in the cooling therein will be ata certain temperature generally approximately the temperature of the surrounding air. Upon starting the engine in operation, the water in the water jackets will begin to heat up and will also begin to circulate through the return pipe towards the radiator. The temperature to which the bulb l in this water will be subjected will thus rise gradually causing the liquid in the bulb to expand and move the column of liquid in the capillary tube 3, which in turn produces an increase in pressure 111 the Bourdon spring or-coil, thereby making the latter tend to open out or. unwind and pro viding a movement of the free end 16 of the 'coil, This movement of the free end of; the coil acting through the lever .37 and compen sating coil 39 rotates arbor 31 and the indexhand 30 to a more or less extent, thus causing the index-hand to. indicate the increase in temperature which has taken place. Assuming that the instrument is properly calilJU brated, if all conditions remain the same ex cept the increase in temperature of the water,

I enough to counterbalance the force which is due to the elasticity of the turns 13, l land 15 and which tends to act in the opposite manner and wind or roll up the spring when the latter is unwound by the liquid therein. lVhen this condition exists the proper sensitiveness of the spring is obtained and the condition in question must exist not only when the pointer is on the higher marks of the scale on the dial plate 24, but also when the pointer is on the lowest extremity distarting point of the scale. Hence the necessity for-putting the. liquid into the spring 10, tube 3 and bulb under some initial pressure as abovestated;or adopting an equivalent expedient. If the spring 10 after being wound and connected to the pointer through the coil 39 and arbor 31, were not put under any initial stress to unwind it; that is, if the liquid merely filled it and did not act to overcome the coils and unwind them to the requiredextent, and expansion of the liquid would unroll the spring, but the con traction of the liquid would be followed by the winding up of the spring only until a certain point was reached. If, for example the pointer were. at degrees, and ,theliquid "merely filled the spring 10 without being the pointer would come back to 60 degrees constrained-to unwind it alittl'e' the expansion of the liquid would unroll the spring and make'the pointer go higher. on the scale; but when the liquid cooled and contracted again and go no lower even if the temperature of 'the liquid sustained a further drop. After long use the pointer would not even come back to 60, degrees, because-the spring 10 would gradually become distended permanently and never restore the pointer beyond a few degrees over 60.

I avoid this possible drawback by putting on the spring 10 an initial stress tending to unwind it: p This initial stress can be secured by applying to the liquidin the spring 10,

tube 3 and bulb 1 as much pressure as is needed. If at degrees room temperature, I fill the bulb. tube and spring, removing all air,- and then apply a pressure of 300, lbs. per square inch, the pointer 30, as-

' suming same to be at :70 degrees on the :scale of the dial plate, will move up to about 120 degrees. I then seal up the spring, .tube and bulb; thereby retaining the pressure of the liquid, and I then turn back the pointer on the arbor 31 to 70 degrees again and make it fast to the arbor. If now the temperature in the bulb 1 goes above 70 degrees, the pointer will move above 70 degrees on the scale; and if the temperature in the 'bulb goes below 70, the pointer can go below 70 degrees on the. scale. In other words even when the liquid contracts to let the elasticity of the spring 10 move the pointer below 70 degrees the volume of the liquid will still be great enough to keep the turns of the spring under stress and allow the elasticity of the latter to make the turns follow up the spring is very certain, and the amount of stress of the spring 10 for any temperature below the first indication on.the scale is technically known as under pressure. Of

course, when the tube, bulb and spring are sealed and the instrument cut off from the source of pressure that produces the initial stress on the spring, the liquid does not exert an active pressure from within on the spring 10 at all. The elasticity of the volume of enclosed liquid and the elasticity of the turns of the spring simplv balance each other at any temperature. When the temperature rises, the liquid expands and overcomes the spring till this balance is restored, and the [liquid as it shrinks. The action of the same action takes place when the temperature drops. Obviously the same effect can ing mixture while filling and warming up after sealing. By this method no pressure on the liquid need be employed when the filling operation is being performed.

-A short filling tube 19. may be connected to the fixed end of the spring 10. If this:

tube is used as an inlet, the bulb. tube 3 and spring 10 must first be emptied of air.

be gotten by putting the bulb 1 into a freez-'"" After filling, pressure can also be applied to the enclosed liquid through the inlet 49; and then sealing is effected by pinching the inlet 49 shut and soldering the end of the latter.

In practical use, all rounding the instrument vary greatly: thus as soon as the engine is started, all of theapparatus is subjectto pronounced vibration.- As the engine heats up, :the tube 3, which ordinarily passes somewhere in proximity to it has its own temperature locally increased and the gage part of the instrument of the conditions surv Ill] may be subjected to an increase in temperature if located in proximity to the engine or may be subjected to a reduction in tempera.- ture if located in anexposed position. If

the instrument is utilized' on' an aeroplane V and an ascent has begun, obviously there' will be a-rapid reduction in'the pressure of the atmosphere surrounding the instrument. Variation in the temperature of the 08.1)11- 'lary tube 3 or of the Bourdon spring 10 will cause the liquid within these parts to expand or contract depending upon whether the temperature rises or falls and will efi'cct a movement ofthe free end of the index hand, in addition to the movement caused by variations in the temperature at the bulb, and therefore, would tend to give rise to erroneous readings. However, the volume of the liquid in the tube 3 isrelatively so small that any'local expansion or contraction of the liquid in same due to changes in temper- .ature near it, will not have to be allowed tend to unwind the Bourdon spring more than the temperature of the fluidin the bulb 1 warrants, and therefore, move the index hand to the right a little too much would also tend to more tightly wind up the compensating coil 39 Se as to tend to move'the index hand to the left. By utilizing a coil or spring having proper characteristics, the compensating coil will exactly counteract the spring 10 as respects any movement or the latter due tochanging local temperature and the pointer 30 will thus indicate the true temperature of the'agent in the pipe 4. By properly designing the compensating coil with relation to the Bourdon spring, this result may be closely secured but if further adjustment is needed to secure exact equalization of any errors, the coiled bi-metallic element lends itself particularly to this pur-- pose, as adjustment may be secured by merely soldering together portionsof-the COll adjacent to one end .thepeof, as indicated for example at 50 in Figure 5. This soldering together throws out part of the coil andreduces the movement-for a given change in temperature. I

, While the use of a thermostatic compensating element compensates fortemperature changes within' the gage itself, it cannot be utilized fully to correct for variations in temperatureof the capillary tube between the gage and the bulb .tor the reason thatthis may be subjected to variations in temperature quite difi'erent from those to which the spring 10 is subjected. The capillary tube is insulated from such change as far as-possible by the casing 46 and I further minimize the eflect of changes in term erature within the capillary tube by, ma ing the latter of very small diameter and volume, for instance, by utilizing the construction of capillary tube shown in Figure 4.

I also promote the desired result by making the Bourdon s ring or coil of very substanti'al length an capacity-or volumeas compared with the volume of the capillary tube, with the result that the movements of the spring caused by the local expansion or con traction of the relatively small volume of liquid in the capillary tube, will bevery slight.

To give an example of the proportions of the respectiveparts which may be successfully employed; With a spring 10 measuring 33 inches from its fixed end to its free end and about /4 inch in width, and 20 feet of tubing 3 of .015 inch inside diameter, reshaped as shown, the tubing will hold only A,, of the amount of fluid in the spring; and the spring and tube together will hold only half as much as will be contained in a bulbof conven'ient size, say inch diameter by 1% inches in length. The total volume is small, I may use 1 pint of liquid for filling 100 instruments with no allowance for loss. Furthermore the tube 3 will preferably be under the hood and near the engine where jacket5, and any-local changes in temperature to which it may be subjected may be left out of account alto 'ether. e

The use 'of a long Bourdon spring of numerous turns is furthermore advantageous in this connection as it gives a degree of movement so considerable as to permit the indicating hand to be driven vdirectly therefrom without the interposition of any ,movement multiplying means, such as long lever arms or gears. Thus it will be seen that there is no multiplication of the move- I ment of the index hand with respect to the movement of the free end of the Bourdon spring, and therefore, no multiplication of hand, the resulting errors would be so great 'as to render the instrument unserviceable.

The elimination of multiplying gearing also has the advantages of promoting simplicity of construction and positiveness of action -with elimination of wear and lost motion,

thereby reducing the possibility of objectionable eifects from vibration. The use of the long Bourdon spring resuch slight errors as may occur due to the v sulting in the advantages noted is made possible primarily by the presence of my im-. proved coiled bimetallic compensating element, as the long spring unless compensated for local temperature conditions would-be a source of error greater probably, than any it will approximate the temperature of the 9 error due to the capillary tube. The coiled compensating element is particularly advantageous as it is most compact, capable of adjustment as already described, and may be made of such length as to produce the relatively large range of compensating movement required. The practical employment of the long Bourdon coil in a compact and serviceable gage is furthermore permitted by the novel mode of winding in the form of a multiple helical coil as above de scribed, and-the whole instrument in consequence may be housed in a casing of relatively small depth from glass to back plate.

Owing tothe characteristics of construc- .tion above set forth, it is possible to construct the instrument as a liquid-filled instrument operating upon the principle of expansion of the liquid due to temperature.

changesyas the errors which would otherwise be present in a liquid filled instrument due to local temperature conditions are re-.

moved. It is also thus possible to secure the important advantage of a li uid filled instrument, namely that it is free from the effects of atmospheric pressure and maybe successfully employed without material error/at any altitude. In this respect it possesses marked advantages over air-filled instruments or instruments operating on the.

- vapor tension principle.

If a gas were employed the. instrument would not be practical for aeroplane use; because at high altitudes the gas, owmg to the lower atmospheric pressure and no matter what would be the temperature in thebulb 1, would expand in the spring 10,

- tending both to unwind it and to distend the turns of the spring by swelling out the flat sides of the same. As a. result the mstrument would become too inaccurate be reliable because the movement of the po 1nt-. ;er due to the expansion of the gas m ght introduce an error of a good many degrees. With liquid, there is no tendency contents of" the spring, tube and bulb to expand, because the liquid has no inter nail pressure that would unwindthe spring or swell out the flat sides of theturns if atmospheric pressure falls; and this statement is 'true'for'all'cases, regardless of the extent to which the spring 10 may be caused to unwind to give it some initial stresswhen.

the liquidfirst fills the instrument. -Th'e truthof this statement is due tothe fact that even though the liquid fis supplied to the instrument under pressure, thatpressure takes. efiectas above described by stressin *and unwinding the spring 10, till the el sticity o'f the liquid enclosed in the Bour on '1 spring and the elasticity of the turns 13, 14:1andj15'are balanced and there is no factor present corresponding to the. internal pressure of a as to affect the instrument in 'c'aseof aall'inat-mospheric'presof the sure i and impair the accurate functioning of the various parts. My invention moreover realizes 'an advantage over alr-filled and vapor filled 1nstruments in being dead-beat or free from the effects of' vibration, a very necessary quality in an indicating instrumentfor use on a vehicle as it makes possible quick and accurate reading thereof. The vapor type of instrument. is particularly objectionable in this regard as any vibration of the bulb or even of the capillary tube will result in bodying numerous novel features, it is to be understood that I do not wish to be limited I in all cases to the use of all of such features as certain of them may be usefully employed separately or without all of the others. The several features do, however, interact. and modify the action of each other 1n such a way that an instrument, particularly for use under the conditions named as upon an aeroplane or automobile, is most satisfactorily constructed by embodying all or substantially all of these features in combination. As modifications may be made in the illustrated embodiment of my invention, I' do not intend to limit myself tothe specific construction set forth but intend to cover any invention broadly in whatever -rformits principle may be embodied. H

The present application is a continuation in part of my application Serial No, 82,518,

for temperature-"indicating system for internal combustion engines, filed March 6, 1916, nowP-a-tent' No. 1,430 688. s

Having thus described my invention, I claim:.-

1. A tubular pressure responsivejeleme'nt for gages wound into. compound helical form, some of the coils of the tube being .wjound .in anfi-opposite axial direction to other of the c'oils but all of the coils being gound in the same circumferential direcon. W I 2. A pressure responsive element for gages comprising a plurality of sets" of tubular helically wound coils connected end. to end to providea continuous passage-way therethrough different sets of -coils being wound in difl'erenbaxial direction but in the same circumferential direction.

3. In a gage, a support, a pressure responsive element comprising a flattened tube fixed at one end to said support and wound in relatively large turns in a direction away from said support and then in smaller turns in the same rotary direction back towards said support, and an indicating element operat-ively connected with the free end of said tuber g 4. In a gage, an indicating element, a pressure responsive element comprising a flattened tube fixed at one end to a supportand wound in relatively large turns in a direction away from said support and then in smaller turns in the same rotary direction back towards said support, a lei-metallic coil within the inner series of turns of said tube, a connection .between one end of said coil and the free end of said tube, and a a 'connection between the opposite end of said coil and'said indicating element. 5. In a gage, the combination of a hellcally coiled tubular pressure responsive ele-' ment, a helically coiled bi-metallic compensating element connected at one end to one end of said pressure responsive element, the helixes formed by said elements beingcO- I axial and said compensating element being rotatable member.

interior to the helix ofl the pressure responsive element, and an indicating element connected to the free end of said bi-metallic compensating elementE 6. In a gage, the combination of a Bourdon spring wound into compound helical form. an indicating member operated thereby, and a helically wound bi-metallic strip for modifying the action of said Bourdon spring upon said indicating member,

the helix formed by the lei-metallic strip being coaxial with the helix formed by said Bourdon spring. and interior thereto.

7. In a gage, the combination of a heli;

call y wound Bourdon spring, an indicating member operated thereby; and a helically wound bi-metallic strip mounted substantially concentrically with i-espect to said Bourdon spring, and arranged to modify the action of said Bourdon spring upon said in the axis of said helically coiled compensating member, and an operative connection between said compensating member and said 9, In a distance type thermometer, the combination of a Bourdon c011 wound nto compound helical form, a bulb and a capillary-tube connecting said bulb and coil, said coil being of such length as to have a large volume compared with the volume of the capillary tube, an indicating member arranged to be actuated by said coil, and a compensating member adjacent to, said coil and arranged to act upon said indicating member in opposition to the actionpf said coil thereonwhcn subjected to local temperature variations.

10. In a distance type thermometer, the

combination of a helically wound llourdon coil having multiple turns, a bulb, a capiland tube being completely filled with a thermally expansible liquid, an indicator operativcly connected with saidcoil in such a way a; to have normally the same angular movement as the angular movement of the end of the coil, and a compensating element wound int'o helical form and placed within the helix formed by theBourdon coil and arranged to act upon said indicator in opposition to the action of said coil, said element being sensitive to local temoerature changes so as to compensate for t e effect of such changes upon said coil. V

12. In a distance type thermometer. the combination of a long helically wound Bourdon coil, said coil consisting of aplurality ofsets of turns, different sets being wound in different axial directions but in the same circumferential direction, a bulb, a capillary tube connecting said bulb and coil, said coil, bulb and'tube being completely filled with an expansible liquid, the volume of liquid contained in said coil being large compared with the liquid" in the capillary tube, a bi-met'allic compensating element wound into helical form and placed within the helix formed by said Bourdon coil, and an indicator directlyconnected to said coil by means of said compensating element and without the interposition of movement multiplying mechanism, said compensating elementacting upon said indicator in the 0pposite direction to the action of the coil thereon when the compensating element and coil are subjected to local temperature variations.

13. In a distance type thermometer, the combination of a helically wound Bourdon coil having a large number of turns, a bulb,

a thermally insulated capillary tube connect- I ing said bulb and coil, said coil, capillary tube and bulb being completely filled with thermally expansible liquid, and indicator having direct operative connection with said coil 'WlthOllt the interposition of movement 7 multiplying gearing, and a compensating elelocal temperature changes, a bulb outside of said casing, and a tube connectingsaid bulb and Bourdon coil.

, 1 5. Inagage, the combination of a fixed support, a rotatable arbor, an indicator thereon, a bi-metall'c coil surrounding said arbor and connecte thereto at one end a Bourdon coil surrounding said compensating coil and connected at its free end to the free end of said compensating coil, the other end of said Bourdon coil being mounted upon said, fixed support. t

16. Ina gage, the co bination of a rotatable arbor, an indicator, mounted thereon, a

hollow pressure responsive element and a compensating element, both in coiled form and surrounding said arbor, an end ofone of said coils being connected to' the arbor and one end of theother coil being connected to a? fixed support, the other ends of u said coils being connected respectively to the opposite ends of) a: lever movably mounted on saidarborfi. g

17. Ina gage,"the combination of a casing having a back plate with a' recess therein, a bearing plate extending across said recess,- an arbor having its. rear end journaledin said bearing platefmeans forming a bearing for the front end of said arbor, an-indicator carried by said arbor, a helical Bourdon spring having turns of equal diameter surrounding said arbor and having one end con;

nected 'tosaid back plate, and means 'forming an operative connection ,between the other end of said Bourdon spring and said arbou 18. In a gage the combination of a casing, a back blate for the casing, spaced supports extending from the back plate towards the front ofthe casing, a dial fixed to'the supports, an arbor having a front journal bearw ing carried by the dial and having a rear journal bearing on the back plate between said supports, a pointer carried by the arbor,

and operating means for the arbor mounted between the dial and back plate.

19. In a gage, the combination of a pointer, a compensating element having one end rigid with said pointer, a pressure responsive element connectedto the other end of said compensa ting element, the pressure responsive element comprising a helicall'y coiled Bourdon spring having a relatively .large number of turns, and a capillary tube communicating with said pressure responsive element, both the tube and said element being filled with an expa-nsible liquid, the capacity of said element being large relative to the capacity of the tube.

20. A distance type thermometer having a bulb, an indicating gage, and corrugated ca illar transmission tubin connectin said-bulb and gage.

' 21. In combination, an indicating member,-

a pressure sensitive member for operating the same, a 'member for subjecting said pressure selfsitive member to pressure variations, and capillary tubing provided with one or more longitudinal depressions for transmitting the pressure variations of said lastmentioned member to said pressure sensitive member. s i Q 22. In a gage, the combination of a rotatable shaft, an indicator connected thereto,

a member rotatable about the axis of said shaft, a hollow pressure responsive element and a compensating element, both in coiled form and concentric with said shaft, one end of one of said coils being connected to the shaft, and one end of the other of said coils being connected to a fixed support, the other ends of said coils being connected, respectively, to said member in such manner as to act thereon 1n opposlte directions.

23. In a pressureoperated indicating instrument in combinationa Bourdon coil, a

coiled compensating spring substantially coaxial w1th the Bourdon coil, a member pivotally'mounted substantially coaxially with the uBourdon coil and the compensating spring and forming a connection between them,- and an indicator member connected for operation from the compensating spring.

. r 24. In a prcssure operated indicating in- 'strument in combination a Bourdon coil, an indicator element, and'means connectin the indicator element for operation by the ourdon coil comprising acoiled compensating spring mounted substantially coaxiallv with the Bourdon coil and connected at one end withthe indicator element, and rigid 'rotary means mounted "coaxially with the Bon r: don coil and the compensating spring and connectin an end of the Bourdon coil'w'ith an end of the compensating spring."

'25. In a pressure operated indicating id strumentin combination, a Bo'urdon coil, a coiled compensating spring within the Bourdon coil, and a lever pivoted at the center In) I nected to the shaft and a member pivoted 10 coaxially With the shaft and constituting a connection between the compensating spring and the Bourdon coil.

In testimony whereof, I have signed my name to this specification this 8th day of 16 February, 1918. I

HERMAN SCI-ILAICH. 

